Monday, 12 December 2011

Understanding of cultural symbionts in academia

Many modern academic students of cultural evolution seem to share a common problem with understanding how cultural evolution operates. Though some pay lip service to the idea, they don't seem to fully appreciate that culture's relationship with human hosts is a symbiosis.

Some quotes (some of which I have discussed before) illustrate the syndrome:

Kevin Laland and Gillian Brown, Sense and Nonsense (2004, p.253):

Social transmission can occur vertically (that is, from parents to offspring), obliquely (from the parental to the offspring generation; for instance, learning from teachers or religious elders) or horizontally (that is, within-generation transmission such as learning from friends or siblings). Of course, genetic inheritance is exclusively vertical and hence, as social transmission frequently occurs through some combination of these modes of information transmission, cultural evolution may commonly exhibit commonly exhibit quite different properties from biological evolution.

Among humans, genes can only pass unidirectionally from one generation to the next (vertically), normally through intimate contact. But ideas (or “memes”) now regularly pass between individuals distant from each other in space and time, within generations, and even backwards through generations. Through mass media or the Internet, a single individual can influence millions of others within a very short period of time.

William Durham (1991, p.193) says:

genes usually cannot be transmitted independently of the reproduction of their carriers. This constraint obviously does not apply to memes.

We do know that culture is most ungene-like in many respects. Culture has the principle of inheritance of acquired variation (what one person invents another can imitate). We are not necessarily blind victims of chance imitation, but can pick and choose among any cultural variants that come to our attention and creatively put our own twist on them. we don’t have to imitate our parents or any other specific individuals but can always be open to a better idea, or own invention or someone else’s.

Alex Mesoudi, Cultural Evolution (2011) has a similar passage:

One of the more obvious differences between cultural and biological evolution involves the potential transmission pathways each involves. Genetic inheritance is often thought of as being exclusively vertical and biparental, with genetic information transmitted in equal amounts from two parents to a single offspring. In culture, on the other hand, one can learn beliefs, ideas, skills, and so forth, not just from one's biological parents (termed "vertical cultural transmission"), but also from other members of the parental generation ("oblique cultural transmission") and from members of one's own generation ("horizontal cultural transmission").

...though Mesoudi continues by acknowledging:

In fact many of these pathways of cultural transmission have parallels in biological evolution.

...although he fails to mention any of the key phenomena of mutualism, partasitism or symbiosis.

Most of the material above is completely wrong. Symbionts (parasites and mutualists) commonly pass "horizontally" between humans. Parasite genes are shared horizontally by kisses, sex, holding hands and sneezing. Mutualist symbionts and their genes are shared between humans at gardening shops, farms, seed shops and fruit shops. Oblique transmission and transmission "backwards" - down the host generations - work in a similar manner. It should be a matter of acute embarrassment among theorists of social evolution to have missed this.

Such symbiont exchange is by no means confined to humans or other creatures with culture - it occurs ubiquitously in the animal kingdom.

In my experience, many of the misunderstandings of memetics actually turn out to be misunderstandings of how biological evolution works. This example is a case in point.

These academic students of cultural evolution usually go on to say that - because of these differences, we need new models to deal with the situation - and then they go on to develop elaborate extended genotype models to deal with the situation. No! That is not how science is done. The existing models of organic symbiosis handle all these cases just fine. We do not need a raft of new models just to deal with the case of organisms whose genes happen not to be made out of DNA.

Mesoudi's defense of this practice reads:

Nevertheless, most quantitative models of genetic inheritance are indeed based on the assumption of vertical inheritance, making it necessary to construct models tailored specifically to the cultural case.

Not everyone in academia gets this wrong. David Hull, for example was pointing out this mistake back in 1988:

In this connection, commentators often state that biological evolution is always vertical whereas conceptual evolution is likely to be "horizontal". By this they mean that the transmission of characteristics in biological evolution is always from parent to offspring (ie, inheritance). Characteristics always follow genes. In point of fact, biological evolution is not always vertical, even when characteristics follow genes. For example, it is horizontal when bacteria, paramecia, etc. exchange genetic material. Horizontal transmission can even be cross-lineage, as when viruses pick up genes from an organism belonging to one species and transmit them to an organism belonging to a different species.

There are a few cases of recognition of symbiosis:

Most mathematical models of cultural evolution derive from epidemiology. The terminology of "horizontal transmission", "vertical transmission" and "oblique transmission" comes from epidemiology. Epidemiology itself is mostly - though not exclusively - concerned with symbiosis.

Boyd and Richerson (1985) have three sentences on symbiosis. They say:

Horizontal transmission is analogous in some ways to the transmission of a pathogen

...and...

The item of culture being spread horizontally acts like a microbe that reproduces and spreads rapidly because it is "infective" and has a short generation length compared to the biological generation length of the host. Fads and fashions and technical innovations are familiar examples.

Boyd and Richerson (2005, p.165) has a paragraph on symbiosis:

The nonparentally transmitted parts of culture are analogous to microbes. Our immune system evolved to kill microbial pathogens but it also allows us to acquire helpful symbionts. As we know all too well, microbial pathogens are common, despite the sophistication of the immune system. One reason is that we are not the only players in this game. Natural selection helps parasites trick our immune system. Since microbial populations have short generation times and large populations, parasite adaptation can be very rapid. The psychology of social learning is like an immune system in that it is adapted to absorb beneficial ideas but resist maladaptive ones. And, like the immune system it is not always able to keep up with rapidly evolving cultural “pathogens.”

This section is pure memetics. They also implicitly endorse symbiosis in their section on "selfish memes" (p.153-154).

An empirical study of the spread of heroin addiction describes the close resemblance of its dynamics to the spread of disease that requires intimate contact (Hughes and Crawford 19721. Addiction is spread along chains of close friendship. Addicts remain infectious only in the early stapes of addiction, while the p1easurabte aspect of the drug still outweighs the manifest disability of advanced addiction. Only a limited population of susceptible individuals is at risk of acquiring the addiction even if exposed. Many simple epidemiological principles probably apply to pathological cultural traits - e.g., parents notice that the incidence of minor microbial infections and various obnoxious habits in children increase together when they first go to school. Crowded classrooms of young susceptibles are the ideal environment for the spread of pathogens of both types by horizontal transmission among the children!

...and there is a fairly specific endorsement of the idea from Peter Richerson here:

I think it is near to undeniable that cultural variants are sometimes selected to become selfish pathogens along the lines that Dawkins suggested. Since some cultural variants can spread rapidly among people, as in the case of fads, they rather resemble the life cycle of a viral or bacterial pathogen.